FR2501954A1 - PLATE CONTROL SYSTEM FOR A TOOL OR MACHINE AND WORKING ON THE GROUND AND DRIVE CIRCUIT FOR THE SAME - Google Patents

Abstract

THIS PLATE CONTROL SYSTEM, INTENDED FOR A TOOL OR A MACHINE 10 ATTACHED TO A VEHICLE, INCLUDING A CHASSIS 12 CARRYING TOOLS 56 ATTACKING THE GROUND, A COUPLING DEVICE 82 DIRECTS FORWARD, SUPPORT WHEELS 60 MOUNTED ON THE CHASSIS AND WHEEL LIFTING CYLINDERS 71 THEY MOUNTED BETWEEN THE CHASSIS AND THE WHEELS TO RAISE OR LOWER THE CHASSIS FROM THE GROUND, INCLUDES A PLATE CONTROL DEVICE 104 AND CONTROL MEANS. THIS DEVICE IS MOUNTED BETWEEN THE CHASSIS AND THE COUPLING DEVICE IN ORDER TO KEEP THE CHASSIS IN PARALLEL PRINCIPLE TO THE GROUND DURING TRANSPORT AND DURING WORK. A CONTROL LEVER IS PROVIDED THAT ACTS BOTH THE WHEEL LIFTING CYLINDERS 71, AND THE PLATE CONTROL DEVICE 104 AND WHOSE MOVEMENT ALLOWS TO MOVE THE CHASSIS AND THE COUPLING DEVICE RELATIVE TO THE GROUND TO HOLD THIS CHASSIS IN THIS POSITION PARALLEL TO THE GROUND.

Description

2 50 1 9 5 4

  Level control system for tool or machine and cir-

  control cooked for this system.

  The present invention relates to a connection system

  trim plate for a tool or machine and more specifically a trim control system and a circuit

  control for an agricultural tool or machine

  like a tractor, such as a disc harrow.

  Most machines hitched to a vehicle

  tractor have support wheels to be able to re-

  raise or lower the machine from the ground. In addition, longitudinal attitude control means of any type may be present to keep the machine in a position parallel to the ground during its movement.

on this one.

  It has already been proposed to provide a link by

  double-acting adjustable spring between the chassis and the

  positive coupling of the machine, in order to constitute a means making it possible to vary the distribution of the weight in the longitudinal direction and also to take account to a limited degree of the relative movement between the device

  hitch and chassis. An arrangement of this type is re-

  presented in particular in US Pat. No. 2,985,247 of May 23, 1961. Another method for ensuring the attitude control of a machine relative to the ground has involved the use of a jack and spring system, as described in US Patent 3,912,917 of October 14, 1975. In this last patent, mechanical adjustment means are provided, from

  so that the operator or driver must leave the vehicle

  vehicle and ensure manual adjustment of the con-

  trim plate provided on the machine using or-

  hand tils. In addition, the lifting wheels provided on the

  machine are connected to the chassis by pendulum axles.

  With this arrangement, only one hydraulic cylinder is used

  to operate all pendulum axles, which are available

  placed horizontally on the elongated chassis of the machine.

  The movement of the pendulum axles ensures mechanically

  raising or lowering the lifting wheels.

  None of these methods or any other existing trim control system allows trim control while walking. In addition, existing systems require manual adjustment, necessitating the use of hand tools. This is frequently a problem when a machine

  agricultural is used in fields with

  different soil conditions. In addition, the presence of axles

  pendulars on the chassis of a disc harrow

  has a disadvantage in that debris from pro-

  old crop lines and newly turned earth tend to stick to the pendulum axles. This accumulation

  crop product residue hinders meteoric actuation

  pendulum axles and prevents rotation of the

discs themselves.

  An object of the invention is to create a trim control system and a control circuit remedying the

  aforementioned disadvantages and making it possible to resolve the

aforementioned wan.

  The main purpose of the invention is therefore to create

  an advanced trim control system and a

  control circuit intended for a machine coupled to a vdhi-

  cule. The object of the invention is more precisely to

  create a hy-actuated trim control system

  and associated control circuit for machine

tractor hitched to a tractor.

  Another object of the invention is to create a system

  attitude control plate for machine coupled to a track

  allowing adjustment during walking.

  Yet another object of the invention is to create

  an advanced trim control system for stubble

  disc mower or the like eliminating the need for manual adjustment of the machine for soil conditions

different.

  Another object of the invention is to create a system

  improved plate control plate for disc harrows or the like eliminating the need to plan

pendulum axles.

  Yet another object of the invention is to create a control circuit which integrates the movement of the jacks

  for lifting the wheels with the movement of the longitu-

  attitude control line, thereby controlling the lift

and. the plate of the machine.

  The invention therefore relates, under one

  of its aspects, a trim control system for where-

  til or machine comprising a frame intended to support

  tools proper attacking the ground, a device for

  telage pivotally connected to this chassis so as to be able to move around a transverse axis and extending forwardly to a front end which can be connected to a towing vehicle, support wheels mounted on this chassis and movable between transport and working positions, characterized in that it comprises, in combination,

  a longitudinal attitude control device for hand-

  hold this chassis in a substantially parallel position

  on the ground, both in the transport and work positions

  vail, this device being mounted between this chassis and this

  positive coupling, and control means for simultaneously actuating the power source moving the support wheels and the attitude control device, so that this coupling device is moved relative to this chassis when said chassis is raised or lowered on

support wheels.

  The invention also relates, according to another aspect, to a control circuit for raising and lowering a tool or

  a machine in relation to the ground and to maintain this ma-

  in a position substantially parallel thereto, said machine comprising a chassis supporting tools attacking the ground, a coupling device pivotally connected

  to this chassis so as to move around a transverse axis

  sal and extending forward to a front end connectable to a towing vehicle, wheels of

  support mounted on this chassis and movable between po-

  transport and working positions, means for lifting the wheels enabling these wheels to be raised or lowered

  support relative to this chassis, and a longitu-

  attitude control circuit to maintain the chassis in a position substantially parallel to the ground both during transport and during work, this device being mounted between this chassis and this coupling device, characterized in that this control circuit comprises a fluid reservoir, a pump connected to this reservoir for pressurizing this fluid, control means for regulating the flow

  fluid from the pump at a time to the return means

  lifting the wheels and to the as-control device

  flap, and flow distributing means for dividing the flow of fluid directed towards the means for lifting the

  wheels in partial currents of the same volume.

  The description which follows, made with regard to

  attached drawings, given without limitation, will allow

better understand the invention.

  Fig. 1 is a plan view of a dethatcher

  discs with perimeter attitude control system

made according to the invention.

  Fig. 2 is a left elevation view of the

  disc harrow shown in Fig. 1, this de-

  that being represented in its raised position or

transport position.

  Fig. 3 is a view similar to FIG. 2 but showing the disc harrow in its lowered position

or working position.

  Fig. 4 is a schematic representation of a

  control circuit for lifting and checking the

  seat of a machine comprising two hydraulic lifting cylinders

  hydraulics and a longitudinal attitude control cylinder.

  Fig. 5 is a schematic representation of a

  alternative embodiment of the control circuit for the

  - raising and controlling the attitude of a machine comprising a folding chassis and comprising several hydraulic lifting cylinders and a longitudinal cylinder for controlling the attitude. Referring now to Figs. 1 to 3, we

  see that a 10-disc disc harrow has been shown

  carrying a frame 12 made of tubes, having the ge-

  of a rectangle with rounded angles. The chassis 12 is shown in the form of a foldable assembly in three parts comprising a main section 14, a right side section 16 and a left side section 18. Although the chassis 12 is represented in the form of a foldable assembly comprising three sections and can be folded by means of hydraulic cylinders 20 and 21 and support bars 22 and 23, the invention would be equally applicable

  rigid chassis in one piece.

  The chassis 12 includes front and rear ends 24 and 26 oriented transversely and right and left sides 28 and 30 respectively. Sections of

  elongated tubular frames 32, 34, 36, 38, 40 and 42 extend

  tend in the longitudinal direction of the chassis 12 and constitute

  kill reinforcement and support for tool sets

and the lifting wheels.

  Two sets of right and left tools diverging forward 44 and 46 are mounted below the front end

  chassis 12, and two different right and left tool sets

  giant rear 48 and 50 respectively are mounted

  under the rear end of this chassis 12. The sets of

  tils 44., 46, 48 and 50 are of conventional construction and

  each includes an elongated tubular frame 52, more

  sieurs arms or vertical ages 54 connected at their upper end to the tubular frame 52, and a set or a row of discs 56 rotatably mounted at the lower end of the vertical ages 54. Each elongated tubular frame 52 is fixed to the rectangular frame 12 by bolts

(not shown).

  Discs 56 can be mounted on the chassis

  12 according to a tandem arrangement or with a double decaf

  age. The layout with double offset is described in

  detail in US Patent 3,734,199 of May 22, 1973 and the year

  work group for each of Tool Sets 44, 46, 48 and

  can be fixed or adjustable so as to allow

  tation under different soil conditions.

  Two or more sets of wheels 60 are rotatably mounted below the chassis 12 between the pairs of front and rear tool sets 44, 46, 48 and 50. Each set of wheels 60 includes two load wheels 62, 64 mounted at

  rotation on an axle 66, each pair of wheels being sup-

  carried by a support arm 68 and 69 respectively (see Fig. 2 and 3). The support arms 68 and 69 of each pair are pivotally connected at their upper end to brackets 70 which are permanently fixed to the right and left sides 28 and 30 of the chassis 12 respectively and to the elongated tubular chassis sections 34

  and 40 respectively. The number of wheel sets 60 pre-

  feel on a machine is going to depend on a number of

  factors including the width of the chassis, the weight of this

  it and the type of chassis. Preferably, each pair of support arms 68 and 69 extends downward and rearward relative to the chassis 12. The movement of the support arms 68 and 69 to raise or lower the sets of wheels 60 relative to the ground is provided by lifting means 71 actuated from an energy source. A preferred lifting means 71 of this type consists of a hydraulic cylinder

  which is pivotally connected by one end, by the inter-

  middle of a link console 72 and a pin 73, aux

  support arms 68 and 69. Preferably, the fixing point

  tion is close to the middle of the support arms 68 and 69.

  The opposite end of each of the lifting means 71 actuated from an energy source is connected to the

chassis 12 by a console 74.

  As can be seen in Fig. 2, the hy-

  hydraulics 71 is shown in its fully extended position in which each of the sets of wheels 60 is in

  contact with the ground, the discs 56 being raised in the

  soil cart. This position is called position of re-

  lifting or transport. In Fig. 3, the hydraulic cylinder 71 is shown in a retracted position in which each of the sets of wheels 60 is lifted away from the ground,

  which allows the disks 56 to be in a position

  tion of work. For clarity, in Figs. 2 and 3,

  the tubular frame 52 carrying the discs and the ages ver-

  tical 54 have been removed, and disc 56 has been

shown in dotted lines.

  If we now refer to the front end of the chassis 12, we see that the disc harrow 10 is connected to a conventional drawbar 80 provided on an agricultural tractor by means of a coupling device 82. The coupling device 82 comprises two tubular members 84 and 86 converging towards the front, a cross member 88 which extends between the convergent tubular members -1 84 and 86, and two upper and lower plates 90 and 92

  which are linked together to form a foot

  lage 94. The front end of the tab 94 is drilled to

  receive a coupling pin 96, in order to connect this provision

  coupling device 82 to the coupling bar 80. The coupling device 82 is connected to the chassis 12 by identical pairs of support plates 97, a single plate of a pair being shown. The two pairs of support plates 97 extend downward from the frame 12. They are connected to each other by a hollow support tube 99 at the base and they are fixed on the opposite sides of the sections tubular chassis 36 and 38 at their upper part. The coupling device 82 is connected to these support plates 97 by axes 98, which allows a pivoting movement of the front end of the coupling device 82 around a transverse axis via these axes 98. Each of the axes 98 extends transversely between each pair of support plates 97

  and pivotally supports one end of the tubular members

  converging areas 84 and 86 between these plates.

  A longitudinal attitude control device is provided on a front part of the chassis 12 and acts in combination with the coupling device 82 to maintain the chassis 12 in a position in principle parallel to the ground permanently. Preferably, this device

  trim control 100 is mounted in the center of the stubble

  disc meuse 10. It comprises a first support arm 102, a hydraulic cylinder 104, a spring system 106 and a second support arm 108. The first support arm 102 is pivotally connected to a front frame part 12 by an axis 109, and its forward movement is limited by a stop 110. The stop 110 is fixed to the chassis

  12 and it is arranged in such a way that a connection ri-

  gide is established between the chassis 12 and the holding device

  telage 82 when the first support arm 102 is applied against this stop 110 and when the disc harrow 10

  is in its transport position.

  The first support arm 102 extends downward and rearward relative to the frame 12, and it is connected

250 1 9 5 4

  pivoted by an axis 111 at one end of the hydraulic cylinder

  104. A piston rod 112 extends from the other ex-

  end of the hydraulic cylinder 104. This piston rod 112

  is coaxial with spring system 106 and enters it

  him. Spring system 106 includes a coil spring (not shown) which is held in place by a

  elongated connecting bolt 114, which is screwed into the

  piston age 112. The hydraulic cylinder 104, which is

  preferably a double-acting cylinder, is mounted in line with

  spring system 106, and both are tilted up and back by the second support arm 108. This second support arm 108 is pivotally connected at one end to the spring system 106 by means of an axis 116, and it is rigidly fixed at its other end to a cross member 118. The cross member 118 is itself fixed

  between the tubular frame sections 36 and 38 as shown

very in Fig. 1.

  The first support arm 102 also carries an adjustable turnbuckle or tie rod 124 mounted by means of a console 122. This adjustable tie rod 124 is pivotally mounted between the console 122 and the cross member 88. It can be adjusted

  by the operator or the driver when the dethatcher has

  ques 10 was connected to the drawbar 80. During the pro-

  conventional coupling stops, the driver moves the tractor back to the disc harrow 10, which rests

  normally on the ground as shown in Fig. 3. The con-

  ducteur then connects the coupling device 82 to the coupling bar 80 and actuates a control lever provided in the tractor cabin, to raise the machine to the

  transport position visible in FIG. 2. When the ma-

  china is in the transport position, the driver manually adjusts the rigging screw or pulling 124 until the chassis 12 is parallel to the ground. This turnbuckle 124 allows the disc harrow 10 to be connected to tractors including

  the drawbars 80 are at different heights

  annuities vertically from the ground.

  Referring now to Figs. 4 and 5, it can be seen that two different embodiments of control circuits have been shown for controlling the operation of the lifting device 71 actuated by an energy source and of the longitudinal attitude control device 100, so as to maintain the disc harrow 10 in a position substantially parallel to the ground both during work and during transport. The control circuit shown in FIG. 4 includes a reservoir 130, a pump 132, a control valve 134 which serves as a control valve

  valve, 136 flow distributor, two hydraulic cylinders

  lifts for wheels 71 and 71 ', a control cylinder

  plates 104, which are all connected together by con-

  lines 138, 140, 142, 144, 146 and 148. The lines 138 and

  connect the flow distributor 136 to the return cylinders

  lifting of the wheels 71 and 71 ', while the duct 142 connects the control valve 134 to the attitude control cylinder 104. The ducts 144, 146 and 148 connect the opposite ends of the lifting cylinders for the wheels 71 and 71' and the attitude control cylinder 104 respectively to the reservoir 130. Preferably, the conduits 144, 146 and 148 penetrate into the control valve 134 and pass through it, so that the direction of flow of the fluid can be reversed. This feature allows the wheel lift cylinders 71 and 71 'and the attitude control cylinder 104 to be actuated

  in either direction. The control valve 134 is de-

  placed by means of a control lever 150. The physical connection

  existing between the control lever 150 and the valve

  134 is indicated by dotted lines for more

  plicity. In operation, when the control lever 150 is moved in one direction, the control valve 134 is brought into an open position and the pressurized fluid from the pump 132 flows through this control valve 134. In leaving the control valve 134, the current is divided into two parts, one part entering the duct 142, while the other enters the flow distributor 136. This distributor 136 can be a division and combination distributor of conventional type , which divides the flow into equal volumes whatever

  pressure differences in lines 138 and 140.

  This gives us the certainty that the pistons that are

250 195 4

  in the two wheel lifting cylinders 71 and 71 'go

  move at the same speed. The piston of the longitu-

  The attitude control line 104 is also controlled so as to move substantially at the same speed as the pistons of the wheel lifting cylinders 71 and 71 '. We

  can achieve this result by providing a foreign orifice

  regulation 154 either in the duct 142 or at the entry of the

  attitude control rin 104. Preferably, a fixed control orifice should be used, in order to maintain a

  predetermined constant pressure in the duct 142.

  There is shown in FIG. 5 a variant of

  Lisation of control circuit for the disc harrow 10. According to this embodiment, a reservoir 155 is connected to a pump 156 which can ensure the pressurization of the fluid and its routing towards a control valve 160. The valve control 160, which is preferably four-way and three positions, is actuated by movement of a control lever 158. The fluid passing through the control valve 160 is directed to two sources. Part of the fluid enters a distributor 162 such as a division and combination distributor, which is capable of dividing the flow of fluid into two equal volumes regardless of the pressure differences in the connecting conduits 184 and 188. The presence of equal fluid volumes in the conduits 184 and 188 provides the certainty that the lifting cylinders of the wheels 164, 166, 168 and 170 will all operate at the same speed, that is to say that the pistons of these cylinders

  will move at identical speeds. The rest of the

  bit of fluid from control valve 160 is di-

  rigged through a conduit 190 and a check valve 178 to a longitudinal attitude control cylinder 172. As

  previously indicated with reference to FIG. 4, an orifice

  throttle 182, which is preferably a fixed orifice, is provided in the duct 190; it is used to throttle the flow so that the piston which is in the attitude control cylinder 172 moves at the same speed as the

  pistons of the wheel lift cylinders 164 - 170.

  The control system also includes two additional check valves 174 and 176, provided in the conduits 184 and 188 which connect the flow distributor 162

  to the wheel lifting cylinders 166 and 168. The purpose of the cla-

  retaining pets 174 and 176, as well as that of the check valve

  retainer 178 provided in the duct 190, is to allow the

  fluid flow in one direction. The check valves 174 - 178 are brought under the effect of the pressure into an open position from a position normally

  closed. However, these check valves 174 - 178 will

  putting a flow in the opposite direction of the fluid through the conduits 184, 188 and 190 respectively when the pressure of the fluid in a pilot conduit 180 which can be put in circuit exceeds a predetermined value. The appearance of

  these pressure values will be explained briefly below

  after. In Fig. 5, the two lifting cylinders for the upper wheels 166 and 164 are connected together in series by a duct 186, and the same is true for the two lifting cylinders for the lower wheels 168 and 170, which are connected by a duct 189. This series connection allows simultaneous displacement of the pistons in all the cylinders, so that the chassis of the disc harrow can be raised or

  lowered while remaining in a horizontal plane. Final-

  ment, three conduits 192, 194, 196 connect the cylinders of

  lifting of the wheels 164 and 170 and the as- control cylinder

  seat 172 to tank 155 via valve

160.

  When the control lever 158 is moved in a second direction, the control valve 160 is brought into a position in which the direction of flow of the fluid is reversed, that is to say that this fluid is directed towards the

  opposite ends of the double wheel lift cylinders

  ble effect 164 - 170 and of the attitude control cylinder 172.

  When the control valve 160 comes to occupy this new

  position, an abrupt change in pressure transmitted through

  firing of the pump 156 is detected by the pilot conduit 180,

  and the check valves 174 - 178 are open. This or-

  greenness of the check valves 174 - 178 allows the pistons which are in the cylinders 164 - 172 to move in opposite directions and to return the fluid which is on their left side to the tank 155, through the distributor

  flow 162 and the control valve 160.

  We will now describe the corresponding operation.

  in this variant embodiment.

  If one starts from a condition in which the disc harrow 10 rests on the ground, so that the

  discs 56 are in contact with the ground surface, the cir-

  control baking shown in FIG. 5 works as follows. When the control lever 158 is moved in one direction, the control valve 160 is actuated, so that the pressurized fluid from the pump 156 flows through the control valve 160. This pressurized fluid

  will then be divided into two parts, one of them

* coming in the duct 190, while the other arrives in the flow distributor 162. This distributor can be of the conventional division and combination type, which divides the flow into equal volumes whatever the pressure differences in the pipes 184 or 188. It is thus certain that the pistons of the wheel lifting cylinders 166 and 168 will move at the same speed. When the pistons of the wheel lift cylinders 166 and 168 start to move, they discharge pressurized fluid through the conduits 186 and 189 respectively into the lift cylinders

  wheels 164 and 170 respectively.

  The simultaneous output of the pistons of the return cylinders

  lifting the wheels 164, 166, 168 and 170 will bring the wheel sets 60 into contact with the ground and will lift the chassis

  to the transport position shown in FIG. 2.

  At the time this occurs, the pressurized fluid which

  is in the duct 190 will pass through the check valve

  178 and the hole 182 to reach the longitu-

  plate control line 172. Here again, hole 182

  allows the plunger of the attitude control cylinder to

  place at the same speed as the pistons of the return cylinders

  lifting of the wheels 164, 166, 168 and 170. The fluid which arrives there causes the exit of the attitude control cylinder 172, so that

  the first support arm 102 pivots towards the front of the chassis 12, which brings the turnbuckle or tie rod 124 in a vertical position. Because of this position

250 195 4

  vertical of the turnbuckle 124, we are sure to obtain a

  stable condition for chassis 12 while dethatching

  disc motor 10 is in the transport position.

  To lower the disc harrow 10 to its working position, the control lever 158 is moved in the opposite direction. Due to this movement, the control valve 160 directs the fluid in the opposite direction through the

  conduits 192, 194 and 196. Any sudden variation in the pressure

  sion in the conduits 192, 194 and 196 will be detected by the pilot conduit 180, which is connected to the conduits 184, 188 and 190 by the check valves 174, 176 and 178. These check valves 174, 176 and 178 are arranged so as to allow the passage of the fluid in only one direction, so that a predetermined pressure can be maintained in the

  system. When a sudden change in pressure is detected

  ted in the pilot duct 180, the valves 174, 176 and 178 are open, so that the flow in the opposite direction from the

  fluid in conduits 184, 188 and 190 is possible.

  When the pistons of the wheel lifting cylinders 164, 166, 168 and 170 move to the left, the sets of wheels 60 will be raised away from the ground and the chassis 12 will be lowered relative to the ground. Simultaneously, the piston of the attitude control cylinder 172 will return to its cylinder, which will move the first support arm 102 rearward relative to the chassis 12. As a result of this action, the turnbuckle 124 will move on a journey in

  arc to take a more inclined position, hand-

  holding the chassis 12 in a substantially parallel position

on the ground.

  One of the advantages of this as-

  sophisticated is that "dynamic" adjustments can be made during work

  by simply moving the control lever 158.

  Although the invention has been described in connection with certain specific embodiments, it will be understood

  that modifications can be made to it, in the

  main technical equivalences without departing from its framework.

2 50 1 9 5 4

Claims (12)

  1.- Plate control system for tool or machine comprising a chassis intended to support - tools proper attacking the ground, a coupling device pivotally connected to this chassis so as to be able to move around a transverse axis and extending forwardly to an anterior end which can be connected to a   towing vehicle, support wheels mounted on this chas-   sis and movable between transport and work positions and a source of energy to move these wheels   support, characterized in that it comprises: -   a) a longitudinal device for controlling the   plate (100) to hold this chassis (12) in a posi-   tion substantially parallel to the ground both in the posi-   transport and work, this device being mounted between this chassis and this coupling device (82); and   b) control means for simultaneously actuating   the energy source (71, 71 ', 164 - 170) moving the support wheels (62, 64) and the attitude control device (100), so that this coupling device is displaced relative to this chassis when said chassis is   raised or lowered on the support wheels.   2.- Plate control system according to the re-   vendication 1, characterized in that the communication device trim plate includes: -   a) a first support arm (102) connected to pivo-   tement at one end to a front part of the chassis (12), b) a second support arm (108) fixed at a point on the chassis located behind this first support arm, c) a hydraulic cylinder (104) coaxially connected to a spring system (106), this hydraulic cylinder being   pivotally connected to this first support arm and this system   spring plate itself being pivotally connected to the second support arm, and d) a tie rod (124) or the like pivotally mounted between a central part of the first support arm and the coupling device (82), for retaining angularly this   coupling device with respect to the front part of the chassis sis. 2 50 1 9 5 4   3.- Plate control system according to the re-   vendication 2, characterized in that this tie or the like   consists of an adjustable turnbuckle or tie rod (124).   4.- Plate control system according to the re-   vendication 2, characterized in that the spring system   (106) includes a compressible spring.   5.- Plate control system according to the re-   vendication 1, characterized in that the control means   is a hydraulic control circuit.   6.- Plate control system according to the re-   vendication 2, applied to a machine comprising a provision   coupling hitch connected to a front end of the chassis   to be able to undergo a vertical pivoting movement   around a transverse axis, this coupling device comprises   both hitch arms extending towards the front of the chassis and provided with fixing means provided at one end for fixing to a towing vehicle, these fixing means being able to move vertically relative to this chassis when the coupling device pivots about this transverse axis, and in which the support wheels are displaced by hydraulic cylinders, characterized in that the control means serve to actuate these hydraulic cylinders (71, 71 ', 164 - 170) of the wheels and the attitude control device (100, 104, 172) jointly, to move the coupling device (82) relative to the chassis (12) when the latter is raised or lowered on the support wheels (62, 64).   7.- Plate control system according to the re-   vendication 6, characterized in that the hydraulic cylinder   longitudinal (104, 172) is mounted in parallel with the   hydraulic wheel rins (71, 71 ', 164 - 170).   8. A coupling system according to claim 6, characterized in that the control means comprise a single control lever (150, 158) capable of controlling   both the hydraulic wheel cylinders (71, 71 ', 164 -   ) and the attitude control device (100, 104, 172) 9.- Control circuit for raising and lowering a tool or a machine relative to the ground and for maintaining this machine in a position substantially parallel to 250 1954   the latter, said machine comprising a chassis supporting tools attacking the ground, a coupling device pivotally connected to this chassis so as to move around a   transverse axis and extending forward to an extreme   front mite which can be connected to a towing vehicle, support wheels mounted on this chassis and movable between   transport and working positions, means of   wheel lifting to raise or lower these wheels   of support with respect to this chassis and a longitu-   attitude control bit to maintain the chassis in a position substantially parallel to the ground both during transport and during work, this device being mounted between this chassis and this coupling device, characterized in   what this control circuit includes -   a) a fluid reservoir (130, 155), b) a pump (132, 156) connected to this reservoir for pressurizing this fluid, c) flow control means (134, 160) for adjusting the flow of the fluid from the pump both to the wheel lifting means and to the attitude control device, and d) flow distributing means (136, 162) for   divide the flow of fluid directed towards the means of.   vage of the wheels in partial currents of the same volume.   10.- control circuit according to claim 9, characterized in that the flow control means comprise a control lever (150, 158) connected to a control valve (134, 160). -   11.- control circuit according to claim 10, characterized in that the control valve (134, 160) is a four-way direction control valve and three positions.   12.- control circuit according to claim 9, characterized in that the flow distributing means   (136, 162> include a division and combi distributor   house capable of dividing the fluid stream in two   equal volumes or in greater number of equal volumes.   13.- control circuit according to claim 9, adapted to a machine comprising hydraulic cylinders 0 1 9 54   wheels capable of raising or lowering the support wheels   port relative to the chassis and a longitudinal cylinder   trim plate mounted between said chassis and the device   coupling, characterized in that it comprises -   a) a control valve (134, 160) mounted between the pump (132, 156) on the one hand and the hydraulic wheel cylinders (71, 71'i 164 - 170) and the attitude control cylinder   (104, 172) on the other hand, to ensure the regulation of the movement   ment of the fluid through these jacks, b) a control lever (150, 158) which can be actuated by hand, connected to this control valve for its actuation, and   c) a splitter with division and combination of   bit (136, 162) mounted between the control valve and the hydraulic wheel cylinders, to divide the fluid stream into   partial currents having equal volumes.